V2 Theme generator and doc updates

[endigo9740]

Linked Issue

Closes #1781

Description

• Updates the getting started instruction @ /docs/get-started (manual tab)
• Updates the Themes documentation @ /docs/themes
• Updates the theme generator install documentation @ /docs/generator
• Updates the theme generator to output the v2 CSS-in-JS format

Changsets

Instructions: Changesets automate our changelog. If you modify files in /packages/skeleton, run pnpm changeset in the root of the monorepo, follow the prompts, then commit the markdown file. Changes that add features should be minor while chores and bugfixes should be patch. Please prefix the changeset message with feat:, bugfix: or chore:.

Checklist

Please read and apply all contribution requirements.

• This PR targets the dev branch (NEVER master)
• Documentation reflects all relevant changes
• Branch is prefixed with: docs/, feat/, chore/, bugfix/
• Ensure Svelte and Typescript linting is current - run pnpm check
• Ensure Prettier linting is current - run pnpm format
• All test cases are passing - run pnpm test
• Includes a changeset (if relevant; see above)

[changeset-bot]

⚠️ No Changeset found

Latest commit: c489c61

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

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Name	Status	Preview	Updated (UTC)
skeleton-docs	✅ Ready (Inspect)	Visit Preview	Aug 3, 2023 5:13pm

[endigo9740]

@AdrianGonz97 I'm adding you as a reviewer to ensure all technical details are correct.

@niktek I'm adding you to verify the CLI follows this instruction

@Sarenor I'm going to ping you as well to review the general flow of the information and to help proofread.

I've rewritten large portions of the pages so it can't hurt for everyone to proof this.

[endigo9740]

@AdrianGonz97 I did one more pass through to improve some of the text. I also implemented a section on the Theme Generator page noting the v1 to v2 migration process. I plan to write up a proper migration guide on GitHub in around launch, so we can include both the guide and tool link straight from that page soon.

Unless you see anything else I think we're ready to merge this.